Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 322 PM EDT Fri Jul 10 2015 Valid 00Z Sat Jul 11 2015 - 00Z Mon Jul 13 2015 ...Severe thunderstorms and flash flooding possible for portions of the Ohio valley and central Appalachians this evening... ...Flash flooding possible for portions of the northwestern U.S... A wave of low pressure along a surface frontal boundary will move eastward across the central Appalachians and into the Mid-Atlantic states tonight into Saturday morning. Showers and thunderstorms are forecast to accompany this low eastward, focused by a surface warm front. The Storm Prediction Center is forecasting a slight risk of severe thunderstorms tonight across portions of the Ohio valley and central Appalachians. Flash flooding is also possible as any thunderstorms could produce locally heavy rainfall. This area of low pressure and the area of most widespread shower and thunderstorm activity will move southeastward to the southern Mid-Atlantic coastline by early Saturday evening, before moving offshore. A warm front will drift northward across the central U.S. through the weekend. The front will be located from the central plains into the Mid-Mississippi valley tonight and will move into the northern plains and Midwest Saturday into Sunday. This warm front will be the focus for a few potential areas of showers and thunderstorms, generally along and north of the frontal boundary. An upper-level trough along the West Coast will not move appreciably through the short range forecast period. Areas of upper-level energy will eject from the trough and move across the western U.S. over the next couple days, which will assist in the development of showers and thunderstorms. Shower and thunderstorms activity will be more widespread in some areas where these upper-level disturbances and topographical influences can combine to focus the convective activity. This will be the case across portions of the interior Northwest through tonight, where sufficient coverage of showers and thunderstorms with locally heavy rainfall will result in the possibility of flash flooding for some areas. The northwestern U.S. will remain the focus for daily shower and thunderstorm activity through the weekend as the aforementioned trough remains in place. High pressure will build in at the mid and upper-levels through the weekend across the southwestern U.S., keeping afternoon and evening thunderstorm activity a little more sparse relative to the Northwest. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php